1. Field of the Invention
This invention relates to an improvement of a two-way delivery valve structure of a fuel discharge valve in a fuel injection pump.
2. Description of the Prior Art
A conventional fuel discharge valve of a fuel injection pump installed in a diesel engine is, in general, closed in order to block one end of a fuel injection pipe after fuel is discharged. Therefore, the remaining pressure sealed in the injection pipe becomes a pressure wave and moves to and fro within the pipe. This remaining pressure is often amplified to open the fuel discharge valve to inject fuel again.
Therefore, in order to prevent such an undesirable occurrence as mentioned, the remaining pressure within the injection pipe must be lowered as soon as the fuel is injected. However, if the pressure within the injection pipe is lowered to a predetermined value or less, the next injection of fuel is not smoothly performed. Therefore, it is necessary that the remaining pressure within the injection pipe is regulated to be in a predetermined range. In recent time, an equal pressure valve or two-way delivery valve comprising a check valve is integrally provided to a fuel discharge valve so as to establishing the pressure within the injection pipe generally equal to that of a pressure chamber by releasing the remaining pressure within the injection pipe after the fuel is injected, into the pressure chamber in which the internal pressure is lowered.
For example, Japanese Patent Application Early Laid-open Publication No. Sho 60-119366 discloses an equal pressure valve, in which a plug member with a through-hole formed therein is press fitted to or caulked to an upper end of a tubular guide pin which is integral with a valve closing member as a fuel discharge valve, thereby to establish a preload to a return spring for energizing the closing member toward a valve seat of the plug member.
However, in the conventional equal pressure valve, the plug member is secured to the upper end of the guide pin by pressure fit for caulking as mentioned. Therefore, although it has the advantage in that the preload can be uniformly established, it is difficult to maintain a uniform fitting of the plug member. For example, the fitting position of the plug member is not constant or the plug member is apt to fall. As a result, the preload becomes inconstant and the sitting posture of the closing member becomes unstable. Moreover, since the fuel discharge valve is integral with the guide pin, much difficulty is encountered when the discharge valve is manufactured. The present invention is accomplished in order to overcome the above-mentioned problems inherent in the prior art.